1. Field of the Invention
The present invention relates to an optical card processing apparatus for performing both of or either one of the recording (writing) and the playing-back (reading) of information onto and/or from a card-shaped recording medium (hereinafter, referred to as an optical card) on which information can be optically recorded with use of a light beam and, more particularly, to an apparatus for detecting an inclination of an optical card set on a card holder at the time when recording or reading the information.
The optical card is used, for example, as a recording card of personal medical information, ID card of banks, middle-scale data base or the like.
The invention also relates to a tracking error detecting apparatus in which when information is recorded onto and/or read out of an optical card, a light beam is irradiated onto tracks of the optical card, thereby detecting a tracking error from the reflected light.
2. Description of the Prior Art
In a conventional optical card processing apparatus, as shown in FIG. 24, a holder 91 having a card holding portion on the upper surface thereof is supported by guide rods 93 so as to reciprocate, the holder 91 is reciprocated through a belt 92 by a drive motor 94 which forwardly and reversely rotates, and an optical head 95 to perform both of or either one of the writing and the reading of information onto/from an optical card 1 is provided over the holder 91. The optical head 95 is arranged so as to face the recording track of the optical card 1 and is moved relatively to the card 1, thereby performing the recording and/or reproducing processes of the information.
In the foregoing optical card processing apparatus, when the optical card 1 is set on the holder 91, there is a case where the optical card 1 is obliquely held so that the moving direction of the holder 91 and the direction of the information recording track of the optical card 1 do not coincide with each other. Thus the erroneous tracking operation occurs.
On the other hand, if the optical card 1 is not highly precisely manufactured, a similar problem also occurs. For instance, when the direction of the information recording track is not parallel with the side edge of the optical card 1 and is inclined, even if the optical card 1 has been correctly set on the holder 91, the direction of the information recording track does not coincide with the moving direction of the holder 91.
To prevent such a drawback, the holding position of the optical card 1 needs to be corrected. For this purpose, it is necessary to detect a correction amount, namely, an angle of inclination of the information recording track to the moving direction of the card (hereinafter, simply referred to as an inclination angle of the optical card). However, a special optical system or the like to detect the inclination angle needs to be assembled in the apparatus, causing a problem such that the structure of the apparatus becomes complicated and is enlarged.
On the other hand, as shown in FIG. 25, a tracking error detecting apparatus has a light projecting optical system which is constructed in a manner such that a light beam irradiated from a light projecting source 81 such as a light emitting diode is converted into a parallel light beam by a collimator lens 82, and the parallel light beam is converged by a condenser lens 83, thereby forming a light spot onto the information recording/recorded portion of the optical card 1. The reflected light of the light spot passes through a light receiving optical system consisting of the condenser lens 83, a reflecting mirror 84, an image forming lens 85 and the like and is led to a photo detector 86. Thus, an image of the surface of the information recording/recorded portion is formed onto the photo detector 86.
The optical card 1 is constructed by forming an information recording/recorded layer 15 on a base plate 14 and by further forming a transparent protective layer 15A on the layer 15. As will be explained hereinlater with reference to FIG. 1, a number of pits 19 are formed in a line on each of a number of information recording tracks 17 along track guides 18, respectively, thereby recording information onto those tracks.
The track guides 18 are previously formed in the whole area in the longitudinal direction of the information recording portion and their light reflectances are generally lower than those of the other portions.
FIG. 26 shows the relation between an image of the optical card 1 formed and the photo detector 86. In the diagram, reference numerals 18 and 19 also represent images of the track guides and pits.
The photo detector 86 consists of a photo diode and has two-split square light receiving portions 86A and 86B. Each of the light receiving portions 86A and 86B is arranged so that one side is adjacent to each other. Photo sensing signals of the light receiving portions 86A and 86B are sent to a differentiating circuit 88 through amplifiers 87A and 87B, respectively. Therefore, when the image of the track guide is located on a boundary line of the light receiving portions 86A and 86B in the photo detector 86, the levels of both of the photo sensing signals coincide. However, when the image of the track guide is deviated in either one direction from the boundary line, a difference occurs between the levels of those photo sensing signals, so that the differentiating circuit 88 outputs a track error signal.
FIG. 27 shows a track error signal which is generated when the photo detector 86 traversed an image of a plurality of track guides in the direction perpendicular to their longitudinal direction. In the diagram, d indicates a distance between adjacent track guides 18. R.sub.0 represents a dynamic range of the track error signal. In the tracking control, a tracking error amount is detected by use of the linear portion of the signal in the dynamic range R.sub.0. The condenser lens 83 is driven by an actuator so that this error amount is set to zero.
However, in the foregoing tracking error detecting apparatus, since a track error signal is generated when the image of the track guides traverses the boundary line of the light receiving portions 86A and 86B which is parallel with the image of the track guides, the dynamic range R.sub.0 of the track error signal is determined by a width of each of the track guides 18. Therefore, the dynamic range R.sub.0 larger than the width of the track guide 18 cannot be obtained in principle. Thus, the dynamic range R.sub.0 of the track error signal is small and a controllable region is extremely narrowed. This results in that even when a slight tracking error occurs, a light spot is deviated from the controllable region. In particular, this apparatus is weak to a shock during the operation. In addition, since the dynamic range R.sub.0 is narrower than the distance between the track guides 18, the tracking pull-in operation (pulling into controllable region) at the start of the tracking control and the tracking pull-in operation in the track jumping operation cannot be easily performed and become uncertain, and the like. There are many practical problems as mentioned above.